<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        function countDown(time) {
            var nowTime = +new Date();//返回的是当前时间总的毫秒数
            var inputTime = +new Date(time);
            var times = (inputTime - nowTime) / 1000;//times 剩余时间总的毫秒数
            var d = parseInt(times / 60 / 60 / 24);//天数
            d = d < 10 ? '0' + d : d;
            var h = parseInt(times / 60 / 60 % 24);//时
            h = h < 10 ? '0' + h : h;
            var m = parseInt(times / 60 / 60 % 60);//分
            m = m < 10 ? '0' + m : m;
            var s = parseInt(times % 60);//秒
            s = s < 10 ? '0' + s : s;
            return d + '天' + h + '时' + m + '分' + s + '秒'

        }

        console.log(countDown('2020-5-30 21:37'));
        var date = new Date();
        console.log(date);
    </script>
</head>
<body>

</body>
</html>